The structural properties of β-phase tantalum nanocrystallites
prepared by room temperature magnetron sputter deposition on amorphous
carbon substrates are investigated at atomic resolution. For these
purposes spherical aberration-corrected high-resolution transmission
electron microscopy is applied in tandem with the numerical retrieval of
the exit-plane wavefunction as obtained from a through-focus series of
experimental micrographs. We demonstrate that recent improvements in the
resolving power of electron microscopes enable the imaging of the atomic
structure of β-tantalum with column spacings of solely 0.127 nm with
directly interpretable contrast features. For the first time ever, we
substantiate the existence of grain boundaries of 30° tilt type in
β-Ta whose formation may be well explained by atomic agglomeration
processes taking place during sputter deposition.